The present invention relates generally to wall constructions for building exteriors and is particularly concerned with the type of wall construction wherein a gypsum sheathing is used as the substrate that is attached to the building structure.
It has long been conventional in the construction of exterior walls to utilize as a substrate a gypsum sheathing having treated paper adhered to opposite surfaces thereof. The normal procedure is to then adhere an insulation layer to one of the paper faces of the gypsum substrate, and then an outer finish layer or coat is applied or adhered to the insulating layer to complete the assembly. Although this type of wall construction has generally proven to be satisfactory, extrusive water penetration may cause deterioration of the treated paper on the gypsum substrate, causing same to separate from the gypsum sheathing, hence adversely affecting wall integrity.
In an effort to improve wall integrity, a gypsum sheathing has recently been introduced to the market wherein a non woven fiberglass matte is adhered to the surfaces of the gypsum core in lieu of the conventional treated paper. This product has been marketed under the name "Dens-Glass" (trademark of Georgia Pacific Corporation), and it has been found that the fiberglass matte is more resistant to breakdown or separation as a result of moisture penetration than is the treated paper. However, it has been found that sufficient moisture penetration may still result in deterioration of the bond of the fiberglass to the gypsum core and/or separation of same from the gypsum core. In addition, since fiberglass is not per se alkali resistant, it has been found that where the insulating layer is adhered to the gypsum/fiberglass substrate by use of a cementitious adhesive, as is frequently the case, the fiberglass is subject to alkali attack as a result of the adhesive, resulting in deterioration and/or separation of the fiberglass from the gypsum. Thus, although the fiberglass-faced gypsum has proven to be an improvement over the paper-faced gypsum, the former is still subject to deterioration resulting from excessive moisture penetration and/or alkali attack where certain cementitious adhesives are used in the assembly.
With the present invention, it has been found that if the fiberglass-faced gypsum is coated with a water-based, water-resistant coating, such as a water-based acrylic coating, for example, prior to the application of any adhesive thereto, and the coating is allowed to dry, it establishes a barrier against excessive moisture penetration, and at the same time it protects the fiberglass matte from alkali attack. In addition, since the fiberglass matte is porous, the aforesaid coating will penetrate therethrough to enhance the bond between the fiberglass matte and the gypsum core. By the same token, the aforesaid coating results in a better bond with the adhesive that is applied thereto in order to secure the insulating layer to the substrate, and greatly improves the water resistance of the bond between the fiberglass matte and the gypsum core.
Other objects, features and advantages of the invention shall become apparent as the description thereof proceeds when considered in connection with the accompanying illustrative drawings.